Technology of electronic apparatuses has recently been significantly developed, and increases in density and performance improvement of integrated circuits have been rapidly advanced. Accordingly, printed circuit boards have also been further increased in density and wiring density and developed in surface mounting of components, and thus higher accuracy and performance than ever before have been required. In order to comply with the higher densities and higher performance of integrated circuits, performance improvement of solder resist used as a main material for integrated circuits has been investigated. However, build-up substrates having fine wiring therein have the problem of causing cracking called a “popcorn phenomenon” at an interface between a solder resist and an encapsulating resin, and solder resist having higher heat resistance is required.
With increases in integration of integrated circuits, a nanoimprint method attracts attention as a method for superfine patterning with a line width of 20 nm or less. The nanoimprint method is roughly divided into a thermal nanoimprint method and an optical nanoimprint method. The thermal nanoimprint method includes pressing a mold on a polymer resin softened by heating to a temperature equal to or higher than the glass transition temperature and then releasing the mold after cooling to transfer a fine structure to a resin on a substrate, and thus the thermal nanoimprint method can form a nano-pattern at a relatively low cost and is expected to be applied to various fields. However, the thermal nanoimprint method requires softening of the polymer resin by heating and thus has difficulty in using a polymer resin having a high glass transition temperature and thus has difficulty in application to the electric/electronic field in which higher heat resistance has been required in recent years.
On the other hand, the optical nanoimprint method including optically curing a composition by light irradiation does not require heating of a molding material to which a pattern is transferred during pressing and is capable of imprint at room temperature. Light-curable resins applied to optical nanoimprint includes a radical polymerization type, an ionic polymerization type, and a hybrid type of the two types, and any type of curable resin composition can be used in nanoimprint application. However, a radical polymerization-type light-curable composition is widely investigated because of its wide range of selection of materials.
When in addition to the high-integration integrated circuit, a thin-film transistor of a liquid crystal display, a protective film of a liquid crystal color filter, a spacer, or a permanent film for application to fine processing of members of other liquid crystal display devices is formed by the nanoimprint method, a nanoimprint material capable of achieving high mechanical characteristics, transparency, light resistance, and heat resistance is required, and a material capable of producing a cured product having high heat resistance is particularly required.
For example, an epoxy (meth)acrylate resin having a biphenyl skeleton is known as a material which produces a cured product with high heat resistance and which is useful as a solder resist (refer to, for example, Patent Literature 1), but this resin does not have recently required high heat resistance.